This invention relates in general to the electronic control of a compressed air brake charging system for a tractor trailer vehicle. More specifically, the invention provides a controller which optimizes vehicle performance during system charging and air dryer regeneration cycles.
Air brake systems for tractor trailer vehicles are well known in the art. In a conventional system, the basic components include an air compressor with a governor valve, an air dryer, a supply reservoir tank, air brake control valves, wheel mounted brake chambers, and wheel mounted brakes. In an air brake system, the compressor furnishes the compressed air for brake operation by taking free atmospheric air and compressing it to 100-120 psi. The compressed air passes from the compressor into the reservoir where it is stored until it is needed. The compressed air is held in the reservoir until it is released by the operator via the air brake control valves. When the operator utilizes the air brake control valves, air flows to the brake chambers where its energy is transformed into the mechanical force and motion necessary to apply the brakes.
As the complexity of conventional air brake systems has increased, so has the need for a clean air supply. The potential contaminants that collect in the air brake system consist of water condensed from the atmospheric air supply and a small amount of oil from the air compressor. These contaminants pass into the system in both liquid and vapor form because of the heat generated during compression. Keeping these contaminants out of the brake system is imperative to prevent failures due to brake system valve stoppage or brake line blockage due to frozen water. The purpose of the air dryer is to purify and dry the air which is outlet by the air compressor. In a conventional system, compressed air flows through the air dryer while the compressor is running. The air dryer contains absorbent desiccant material which becomes saturated during use. Therefore, the desiccant must be periodically recycled by heating or other means to expel accumulated water vapor.
Conventional air brake systems require periodic recharging of the air supply reservoir. Under normal operating conditions the air compressor control system has a low limit pressure of about 100 psi and a high limit pressure of about 120 psi. When the pressure in the supply reservoir tank drops below 100 psi the system turns the air compressor on and opens the governor valve. When the pressure in the supply reservoir tank reaches 120 psi the system turns the air compressor off and closes the governor valve. Once the air compressor is turned off the air dryer recycles itself by purging the desiccant bed.
An undesirable condition arises when the vehicle is under maximum operating load and it is simultaneously charging the system or regenerating the air dryer. In this case, some of the engine""s power will be diverted from powering the wheels to powering the air compressor. This is not desirable under a maximum load situation, because a heavily loaded vehicle""s ability to accelerate or climb a long grade would be diminished. In addition, when a vehicle is first started in the morning if the air pressure in the air brake system is low, and the mechanical spring parking brake is engaged, then the vehicle cannot move until the air system develops enough force to disengage the spring. Thus, the operator must wait for a considerable time while the system is brought up to operating pressure before he may move his vehicle.
It is therefore and object of the present invention to provide a system to coordinate air brake system charging cycles with periods of non peak engine performance requirements, and to shorten the charging time for the system upon vehicle start up.
The present invention provides an electronic air charge controller for a tractor trailer vehicle air brake system. The electronic air charge controller includes a micro controller, a first pressure sensor interface coupled to the micro controller, a second pressure sensor interface coupled to the micro controller, and a vehicle control protocol interface coupled to the micro controller. The micro controller, in response to a signal received from the first pressure sensor interface indicative of an air supply recharge condition, a signal received from the second pressure sensor indicative of parking brake engagement condition, and a signal from the vehicle control protocol interface indicative of an engine start condition, supplies a maximum engine speed control signal to the vehicle control protocol interface. The time required to charge the air supply system to the required normal operating level is thereby minimized.
In addition, a transmission sensor interface is preferably coupled to the micro controller. The micro controller does not generate the maximum engine speed control signal unless a signal supplied by the transmission sensor interface indicates that an automatic transmission is in park or a manual transmission is in neutral. An added measure of safety is provided by preventing the engine speed from going to maximum unless the transmission is in a position that impedes vehicle movement.
Still further, to improve operating efficiency, a vehicle load condition signal is supplied by the vehicle control protocol interface to the micro controller. In response, the micro controller supplies a pause air compressor charging cycle signal or a pause air dryer recycle signal to the vehicle control protocol interface, if either the air compressor or air dryer is operating when a high load condition is encountered.